A type of laminate called an FR-4 obtained by laminate molding a prepreg consisting of fiberglass cloth impregnated with an epoxy resin or other resin component is widely used as a typical laminate in printed wiring boards for electronic devices. The term FR-4 is a category established by the U.S. National Electrical Manufacturers Association (NEMA). So-called CEM-3 type composite laminates, which are composed of a core layer of nonwoven cloth impregnated with a resin component, laminated on both sides with surface layers of fiberglass cloth impregnated with a resin component, are also known.
For example, Patent Document 1 below proposes a composite laminate with high interlayer adhesive strength and excellent alkali resistance, heat resistance and punching quality, comprising a resin-impregnated surface material of fiberglass cloth impregnated with resin varnish, affixed to both sides of a resin-impregnated core material of nonwoven cloth and/or paper impregnated with resin varnish, and further clad with a metal foil. In this composite laminate, the resin varnish used in the core material contains a filler combining talc and aluminum hydroxide, with the compounded ratio of talc to aluminum hydroxide being 0.15:1 to 0.65:1, and the aluminum hydroxide is described as being of the boehmite type.
Also, for example, Patent Document 2 below describes a composite laminate with excellent thermal stability and fire retardancy, which is a laminate for printed circuit boards composed of surface layers of resin-impregnated fiberglass woven cloth and a middle layer of fiberglass nonwoven cloth impregnated with a hardening resin. In this laminate, the middle layer is described as containing an aluminum hydroxide of the chemical formula Al2O3·nH2O (wherein n has a value greater than 2.6 and smaller than 2.9) in the amount of 200 wt % to 275 wt % of the resin in the middle layer.
As electronic devices have become lighter and more compact in recent years, electronic parts are being mounted at higher densities on printed wiring boards, and these electronic parts may include multiple LEDs (light-emitting diodes) and the like that require heat dissipation. The problem has been that conventional laminates lack adequate heat dissipation properties as substrates for such purposes. Moreover, the most common mounting method is by reflow soldering, and lead-free reflow solder, which requires a high-temperature reflow process, has come to predominate in reflow soldering because of its low environmental impact. In reflow soldering using such lead-free solder, high heat resistance is required in order to control blistering and the like. It is also necessary to maintain drilling performance. From a safety standpoint, moreover, fire retardancy must be at the V-0 level according to the Ul-94 standard.    Patent Document 1: Japanese Patent Application Laid-Open No. S62-173245    Patent Document 2: Japanese Translation of PCT Application No. 2001-508002